Circular saw

ABSTRACT

A side cutting edge of a tip  20  fixed to the outer circumference of a circular saw blade body  11  has a inflexion point K at a portion at which the tip projects laterally to the greatest distance. An outer-circumferential-side portion of the side cutting edge has a negative radial clearance angle of not less than −1° but less than 0° at the inflexion point, and an inner-circumferential-side portion of the side cutting edge has a positive radial clearance angle of greater than 0° but less than −1° at the inflexion point. By virtue of this configuration, a cut surface having a better surface roughness as compared to that obtained conventionally can be obtained in cutting of a soft material such as wood by use of a circular saw.

TECHNICAL FIELD

The present invention relates to a circular saw used for woodworking andsimilar work, and more particularly, to the shape of side cutting edgesof tips fixed to teeth of the circular saw.

BACKGROUND ART

In a conventional circular saw of the above-described type, side cuttingedges of tips are formed to assume a positive radial clearance anglewith respect to a radial direction. The surface roughness of a cutsurface of a workpiece formed as a result of cutting the workpiece byuse of a circular saw will be considered with reference to FIG. 18. Inan example case in which a workpiece is cut by use of a circular sawhaving 40 flat tips (top bevel angle is zero, face bevel angle iszero)each having a radial clearance angle of 1°, at a rotational speedof 4000 rpm and a material feed rate of 5 m/min, the feed amount per tipbecomes about 0.03 mm, and a theoretical surface roughness Rmaxcalculated on the basis of the feed amount becomes about 0.55 μm.

However, when a wood workpiece (pinus radiata wood) was actually cut byuse of the above-described circular saw, the surface roughness Rmax ofthe cut surface was 86.4 μm, which greatly deviates from the theoreticalvalue. The conceivable reason is as follows. Since wood is afiber-containing material, wood is generally cut through a cuttingmechanism to be described below, with easiness of cutting varyingslightly with the direction along which fibers are cut. That is, whenshear load is produced due to cutting force acting on a rake face,cracks are first generated in the material under cutting such that thecracks extend from the peripheral cutting edge toward the direction ofrotation of the saw and outward with respect to the width direction ofthe saw, and subsequently, chips are produced while being torn from thegenerated cracks. Since the above-described operation is repeated inorder to effect cutting, cracks and depressions remain on the cutmaterial. As a result, the surface roughness greatly deviates from thetheoretical value.

The present invention solves the above-described problems, and itsobject is to provide a circular saw which can reduce the surfaceroughness of a cut surface of a soft material such as wood formed thoughcutting.

DISCLOSURE OF THE INVENTION

In order to achieve the above-described object, the first inventionprovides a circular saw having tips fixed to a plurality of teethprojecting radially outward from the outer circumference of adisk-shaped saw blade body, characterized in that a side cutting edge,which has a inflexion point at a portion at which the side cutting edgeprojects laterally to the greatest width in a front view of the tip, hasa negative radial clearance angle of not less than −1° but less than 0°in the vicinity of the inflexion point of the side cutting edge and onthe outer circumferential side with respect to the inflexion point, anda positive radial clearance angle of greater than 0° but less than 1° inthe vicinity of the inflexion point of the side cutting edge and on theinner circumferential side with respect to the inflexion point.

In the tipped saw according to the first invention having theabove-described structure, since the side cutting edge is formed toassume a negative radial clearance angle on the outer circumferentialside with respect to the inflexion point and a positive radial clearanceangle on the inner circumferential side with respect to the inflexionpoint, there can be obtained a cut surface of lower surface roughness(greater smoothness) as compared with that obtained by use of aconventional saw. Notably, the radial clearance angle of 0° is notpreferable, because the cut surface is likely to be burned. Further,when the outer-circumferential-side radial clearance angle is less than−1° or when the inner-circumferential-side radial clearance angle isgreater than 1°, surface roughness increases.

The second invention provides a circular saw having tips fixed to aplurality of teeth projecting radially outward from the outercircumference of a disk-shaped saw blade body, characterized in that theplurality of tips include in combination the tips according to the firstinvention and second tips, wherein the second tips have an outercircumferential height greater than that of the tips according to thefirst invention and a maximum width narrower than that of the tipsaccording to the first invention.

In the tipped saw according to the second invention having theabove-described structure, the tips according to the first invention andthe second tips are combined so as to perform divided cutting such thatperipheral cutting is performed mainly by the second tips, and a roughcut surface formed as a result of cutting by the second tips issubjected to surface cutting performed by the tips of the firstinvention. As a result, it becomes possible to obtain cut surface ofgood quality, while reducing cutting resistance as compared with thecase of use of a circular saw having the tips of the first inventiononly.

The third invention is characterized in that a mechanism having a higherdamping capability is equipped to the saw blade body of theabove-described circular saw such that at least a portion of themechanism is present in an area between a concentric circle having adiameter 80% the outer diameter of the circular saw and a concentriccircle having a diameter 100% the outer diameter of the circular saw.

This configuration prevents vibration of the saw blade body of thecircular saw. As a result, peculiar cutting noise generated duringcutting upon use of the tips can be suppressed, and cut surface of highquality can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows enlarged front and side views of a tip of a circular sawaccording to a first embodiment of the present invention.

FIG. 2 shows enlarged front and side views of tips of circular sawsaccording to modifications of the first embodiment.

FIG. 3 is an explanatory diagram showing a cutting state in the case inwhich a rake face of a tip has a face bevel angle.

FIG. 4 shows enlarged front, plan, and side views of a tip of a circularsaw which has a inflexion rake face having no face bevel angle.

FIG. 5 shows enlarged front, plan, and side views of a tip which has ainflexion rake face having a face bevel angle that is constantirrespective of position in the radial direction of the saw.

FIG. 6 shows enlarged front, plan, and side views of a tip which has ainflexion rake face having a face bevel angle that changes with theradial direction of the saw.

FIG. 7 shows enlarged front, plan, and side views of a tip of a circularsaw of Test Example 1.

FIG. 8 shows graphs representing the cross-sectional profile of aworkpiece cut by use of a tipped saw of the present invention and thecross-sectional profile of a workpiece cut by use of a conventionaltipped saw, which profiles were obtained in Test Example 2.

FIG. 9 shows graphs representing the cross-sectional profile of aworkpiece cut by use of the tipped saw of the present invention and thecross-sectional profile of a workpiece cut by use of a conventionaltipped saw, which profiles were obtained in Test Example 3.

FIG. 10 shows enlarged front and side views of a tip of a circular sawof Test Example 4.

FIG. 11 shows a graph representing the relationship between materialfeed rate and net cutting power of a tipped saw as obtained in TestExample 5.

FIG. 12 shows a graph representing the cross-sectional profile of aworkpiece cut by use of the tipped saw of the present invention asobtained in Test Example 5.

FIG. 13 shows enlarged front, side, and plan views of a tip of acircular saw of Test Example 6.

FIG. 14 shows a graph representing the relationship between noise leveland ratio da/do (outer diameter of a vibration-absorbing plate/outerdiameter of a tipped saw) as obtained in Test Example 6.

FIG. 15 is a side view showing the entirety of the circular saw of TestExample 6.

FIG. 16 shows a graph representing the relationship between noise leveland rotational speed of a circular saw as obtained in Test Example 7.

FIG. 17 shows an enlarged front view of a tip in which a inflexionportion of a side cutting edge has a deformed shape.

FIG. 18 is an explanatory diagram which is used for calculating thesurface roughness of a material cut by use of a conventional circularsaw.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described with reference tothe drawings. FIGS. 1(a) and 1(b) show a tip, which is a main portion ofa tipped circular saw according to a first embodiment, by means of afront view (view obtained through projecting the tip on a plane Mincluding the rotational axis of the circular saw and the tip of thetip) and a side view.

A tip 20 is provided on a front face 12 a, with respect to therotational direction, of each tooth 12 projecting outward from the outercircumference of a disk-shaped saw blade body 11 of a circular saw (inFIG. 1, the circular saw has an outer diameter of 255 mm, a saw bladebody thickness of 3 mm, and 40 teeth). The tip 20 inclines slightlytoward the front side with respect to the rotational direction tothereby form a rake angle (20° in the illustrated example). A peripheralcutting edge 21 is flat and has a peripheral clearance angle (15° in theillustrated example). As shown in FIG. 1, each side cutting edge 22 ofthe tip 20 has a inflexion point K at a position which is offset fromthe outer circumference toward the inner circumference side by apredetermined distance (1.2 mm in the illustrated example). At theinflexion point K, the tip 20 projects laterally to have the greatestwidth (4.4 mm in the illustrated example). The side cutting edge 22forms straight lines that extend from the inflexion point K towardopposite sides each other. The radial clearance angle on the outercircumferential side of heinflexion point K is negative (−30′ in theillustrated example), and the radial clearance angle on the innercircumferential side of the inflexion point K is positive (10′ in theillustrated example).

In the tip 20, a between an outer circumference end portion 21A and theinflexion point K as measured along the width direction is about 0.01 mm(about 10 μm). Therefore, cracks and depressions generated by the outercircumference end portion 21A are cut over a length L of their entireheights. The theoretical surface roughness Rmax of a cut surface of awood workpiece cut by use of a circular saw having the tip 20 is 76.4μm, which is a value obtained through subtraction of the length L fromthe surface roughness Rmax of 86.4 μm above-mentioned for the case inwhich a wood workpiece was actually cut by use of a conventionalcircular saw. However, when a wood workpiece (pinus-radiata wood) wasactually cut by use of the above-described circular saw at a rotationalspeed of 4000 rpm and a material feed rate of 5 m/min, the surfaceroughness Rmax was measured to be 18.6 μm, which greatly deviates fromthe calculated value of 76.4 μm. That is, cracks and depressionsgenerated upon cutting by use of the circular saw of the presentembodiment were found to be smaller than cracks and depressionsgenerated upon cutting by use of a conventional circular saw whose sidecutting edge has a positive radial clearance angle only. Therefore, whena workpiece is cut by use of the outer-circumference end portion 21A,which is a portion of the side cutting edge 22 having a negative radialclearance angle, the sizes of generated cracks and depressions can bedecreased. In addition, since generated cracks and depressions arecut-removed by an amount corresponding to the widthwise length L, cracksand depressions remaining on a finished surface further decrease insize. Moreover, in the vicinity of the inflexion point K, the workpieceis cut in such a manner that the cut surface is cut lightly andshallowly or is pressed inward. Therefore, conceivably, new cracks arehardly generated on the finished surface.

Next, modifications of the above-described embodiment will be described.

In one modification, as shown in FIG. 2, a peripheral cutting edge 31 ofa tip 30 whose side cutting edges have positive and negative radialclearance angles is formed into a concave shape (FIG. 2(a)) or a convexshape (FIG. 2(b), which shape is symmetric with respect to the widthwisedirection. For the case of the peripheral cutting edge 31 being formedinto a concave shape, the peripheral cutting edge 31 of the concaveshape was found to further reduce the generation of cracks anddepressions that extend outward in the thickness direction of the saw.Further, since the peripheral cutting edge 31 of the concave shapeimproves the stability of the tip 30 in terms of moving straight withrespect to the material feed direction to thereby suppress side run-out,the rake surface can be finished much better. Moreover, as shown in FIG.3, when the rake face of the tip 30 is formed to have a face bevelangle, side cutting resistance can be reduced, so that the flowdirection of chips can be changed to a direction indicated by an arrow(solid line) in order to facilitate discharge of chips.

Next, tips which fall within the scope of the present invention butdiffer from the above-described embodiments will be described. Each ofthe tips shown in the above-described embodiments has a single rakeface. Here, tips T1 to T3 each of which has two flat rake faces 41 oneither side of the inflexion point K, will be described.

FIG. 4 shows a tip T1 which has zero face angle; FIG. 5 shows a tip T2which has a faevel an that is constant along the radial direction of thesaw; and FIG. 6 shows a tip T3 which has a face bevel angle that variesalong the radial direction of the saw. Notably, as a result of formationof a V groove (arcuate groove) along a line G, the rake face has a facebevel angle. These tips T1 to T3 provide effects similar to thosedescribed in relation to the above-described embodiment.

Next, a second embodiment will be described.

The present embodiment is directed to a circular saw in which the tip 20(or the tip 30) of the above-described embodiment and a conventional tipare attached in combination to the teeth 12 of the saw blade body 11,the conventional tip having a rake angle and a peripheral clearanceangle, and an outer-circumferential height greater than that of the tip20, as well as a maximum width narrower than that of the tip 20. Thetips of the above embodiment and the conventional tips may be equal innumber or may differ in number. Further, the tips of the aboveembodiment and the conventional tips may be arranged in accordance witha certain sequence or arbitrarily.

When the tipped saw having the above described configuration is used,peripheral cutting is effected mainly by the conventional tip, and arough cut surface formed as a result of the cutting by the conventionaltip is cut mainly by the tip 20. Since the conventional tip and the tip20 cut the cutting area in a divided manner, cutting resistance can bereduced, and a well-finished cut surface can be obtained through actionof the tip 20.

Next, there will be described specific cutting test examples in whichthe above-described tip was used.

(1) TEST EXAMPLE 1

Five types of test samples of tips (tipped saws of the presentinvention) were prepared. As shown in FIG. 7, each tip had a rake angleof 20°, a side clearance angle of 3°, and a peripheral clearance angleof 15°. An outer-circumferential-side negative radial clearance angle θ1and an inner-circumferential-side positive radial clearance angle θ2shown in the front view were varied among the five types as shown inTable 1, which will be described below. Further, a conventional tippedsaw (having a positive radial clearance angle θ2=60′ only) was preparedas a comparative sample. In each tipped saw, 40 tips were fixed to teeth12 of a saw blade body 11 having an outer diameter of 255 mm, a saw kerfwidth of 4.4 mm, and a saw blade body thickness of 3 mm.

Cutting was performed at a rotational speed (of the tipped saw) of 5000rpm and a material feed rate of 10 m/min. The material of a workpiecewas wood (spruce: conifer), and longitudinal cutting (cutting along thedirection of fibers) was performed. Evaluation items were center-lineaverage roughness Ra, ten-points average roughness Rz, maximum heightRmax, appearance, and texture of cut surface. Quality of cut surface wasjudged through total evaluation of these items. Appearance and texturewere evaluated, while the cut surface obtained through use of theconventional tipped saw was used as a standard (rank: C). When a cutsurface obtained through use of the tipped saw of the present inventionwas slightly better than the cut surface obtained through use of theconventional tipped saw, the cut surface was assigned rank B. When a cutsurface obtained through use of the tipped saw of the present inventionwas considerably better than the cut surface obtained through use of theconventional tipped saw, the cut surface was assigned rank A. Table 1shows test results.

TABLE 1 outer inner center-line ten-points radial radial total averageaverage maximum clearance clearance evaluation appearance textureroughness roughness height angle angle rank rank (rank Ra Rz Rmax θ₁ θ₂(A. B. C) (A. B. C) A. B. C) (μm) (μm) (μm) conventional 60′ C C C 3.530.4 36.7 tipped saw tipped saws −10′ 30′ A A A 1.8 19.0 21.3 of thepresent −30′ 10′ A A A 1.5 15.7 18.1 invention 30′ A A A 1.7 20.4 25.550′ A A A 1.8 21.5 32.3 60′ B B B 2.2 23.1 31.4 −60′ 30′ A A A 1.8 20.325.1

As is apparent from the results shown in Table 1, as to respectiveroughness values, appearance, and texture, the five tipped saws of thepresent invention provided results which are far better than thoseobtained through use of the conventional tipped saw.

(2) TEST EXAMPLE 2

As test samples of tips (tipped saws of the present invention), therewere prepared forty tips each having the same shape as that of the testsamples used in Test Example 1. Each tip had a rake angle of 20°, a sideclearance angle of 3°, and a peripheral clearance angle of 15°; and anouter-circumferential-side negative radial clearance angle of −10′ andan inner-circumferential-side radial clearance angle of 30′, bothmeasured in the front view. The forty tips were fixed to a saw bladebody having an outer diameter of 255 mm, a saw kerf width of 4.4 mm, anda saw blade body thickness of 3 mm in order to obtain a tipped saw ofthe present invention. A conventional tipped saw having conventionaltips attached thereto was prepared as a comparative sample.

Cutting was performed at a rotational speed (of the tipped saw) of 4000rpm and a material feed rate of 5, 10, 20, or 30 m/min. The material ofa workpiece was wood (pinus radiata: conifer), and transverse cutting(cutting along a direction perpendicular to the fiber direction) wasperformed. Evaluation items were center-line average roughness Ra,ten-points average roughness Rz, and maximum height Rmax of cut surface.Table 2 shows test results; and FIG. 8 shows the cross-sectional profileof the workpiece cut at a material feed rate of 20 m/min.

TABLE 2 center-line ten-points manterial average average maximum feedspeed roughness roughness height (m/min) Ra (μm) Rz (μm) Rmax (μm)TIPPED SAW OF THE PRESENT INVENTION 5 1.4 16.4 18.6 10 2.2 24.0 29.6 203.4 32.2 37.0 30 4.4 42.0 58.8 CONVENTIONAL TIPPED SAW 5 4.6 74.4 86.410 6.4 77.2 99.4 20 12.8 163.2 184.8 30 19.4 193.8 265.2

As is apparent from the results shown in Table 2 and the cross-sectionalprofile shown in FIG. 8, as to respective roughness values, the testsample (the tipped saw of the present invention) achieved greatlysmaller values than those obtained by use of the conventional tippedsaw. In addition, as to the cross-sectional profile, the test sampleachieved a better result, with a clear difference from the resultobtained though use of the conventional tipped saw.

(3) TEST EXAMPLE 3

The same test samples of tips as those used in Test Example 2 were used.Cutting was performed at a rotational speed (of the tipped saw) of 4000rpm and a material feed rate of 5, 10, 20, or 30 m/min. The material ofa workpiece was wood (Japanese oak: broad-leafed tree), and transversecutting was performed. Evaluation items were center-line averageroughness Ra, ten-points average roughness Rz, and maximum height Rmaxof cut surface. Table 3 shows test results; and FIG. 9 shows thecross-sectional profile of the workpiece cut at a material feed rate of10 m/min.

TABLE 3 center-line ten-points manterial average average maximum feedspeed roughness roughness height (m/min) Ra (μm) Rz (μm) Rmax (μm)TIPPED SAW OF THE PRESENT INVENTION 5 5.0 97.2 115.2 10 6.4 99.2 124.220 5.8 94.6 123.2 30 7.2 103.6 153.6 CONVENTIONAL TIPPED SAW 5 6.8 116.8148.4 10 8.2 135.2 188.2 20 9.8 140.8 167.6 30 13.2 152.0 174.8

As is apparent from the results shown in Table 3, as to respectiveroughness values, the test sample (the tipped saw of the presentinvention) achieved greatly smaller values than those obtained by use ofthe conventional tipped saw. However since Japanese oak contains vesselsof large diameter, the values of surface roughness becomes relativelylarge, even though the remaining portion is flat, so that the differencefrom the case of the conventional tipped saw may decrease in some cases.In addition, as to the cross-sectional profile, vessels of largediameter could be identified more clearly as compared with the case ofuse of the conventional tipped saw, because, in the case of use of thetest sample, the cut surface is flat except for vessels of largediameter.

(4) TEST EXAMPLE 4

Four types of test samples No. 1 to No. 4 of tips (tipped saws of thepresent invention) were prepared. As shown in FIG. 10, each sample tip50 had two cutting surfaces 51 (first rake angle ψ1, second rake angleψ2). The shape of side cutting edges 52 as viewed in the front view;i.e., the outer-circumferential-side radial clearance angle θ1, theinner-circumferential-side radial clearance angle θ2, the side clearanceangle, and the peripheral clearance angle were varied among the testsamples No. 1 to No. 4 in accordance with combinations shown in Table 4.Notably, the test samples No. 1 to No. 3 fall outside of the scope ofthe present invention, because the outer-circumferential-side radialclearance angle θ1 is positive or zero; and therefore, only the testsample No. 4 falls within the scope of the present invention. Further,in the test samples, two rake faces having different rake angles wereformed in order to provide a two-step radial clearance angle. In eachtipped saw, 40 tips were fixed to teeth 12 of a saw blade body 11 havingan outer diameter of 255 mm, a saw kerf width of 4.4 mm, and a saw bladebody thickness of 3 mm. A conventional tipped saw was prepared as acomparative sample.

Cutting was performed at a rotational speed (of the tipped saw) of 5000rpm and a material feed rate of 10 m/min. The material of a workpiecewas wood (spruce: conifer), and longitudinal cutting was performed. Inaddition to appearance and texture, center-line average roughness Ra,and ten-points average roughness Rz, maximum height Rmax of cut surfacewere evaluated. Appearance and texture were evaluated, while the cutsurface obtained through use of the conventional tipped saw was used asa standard (rank: C). When a cut surface obtained through use of thetipped saw of the present invention was slightly better than the cutsurface obtained through use of the conventional tipped saw, the cutsurface was assigned rank B. When a cut surface obtained through use ofthe tipped saw of the present invention was considerably better than thecut surface obtained through use of the conventional tipped saw, the cutsurface was assigned rank A. Table 5 shows test results.

TABLE 4 outer inner radial radial clearance clearance rake rake sideperipheral angle angle angle angle clearance clearance θ1 θ2 ψ1 ψ2 angleangle No. 1  30′ 60.1′ 20° 30° 3.41° 15° No. 2  10′ 34′ 20° 30° 2.23°15° No. 3  0′ 34′ 20° 30° 3.27° 15° No. 4 −10′ 34′   17.5° 30° 3.45° 15°

TABLE 5 total center-line ten-points maximum evaluation appearancetexture average average height rank rank (rank roughness roughness Rmax(A. B. C) (A. B. C) A. B. C) Ra (μm) Rz (μm) (μm) conventional tippedsaw C C C 3.5 30.4 36.7 No. 1 B B B 2.8 29.4 33.4 No. 2 B A B 2.2 22.930.1 No. 3 A A A 1.7 19.5 22.3 No. 4 A A A 1.7 16.7 19.3

As is apparent from the results shown in Table 5, the test sample of thepresent invention (No. 4) and the test sample No. 3 having anouter-circumferential-side radial clearance angle of 0° provided goodresults for the respective items. Although the test samples No. 1 and 2having two-step positive radial clearance angles provided better resultsas compared with the conventional tip, the results provided by the testsamples No. 1 and 2 were clearly inferior to those provided by the testsamples No. 3 and No. 4. Accordingly, cutting performance is notimproved through mere employment of a two-step radial clearance angle,and the radial clearance angle on the outer circumferential side of thetip must be made negative. Although good cutting performance is obtainedeven in the case of the radial clearance angle on the outercircumferential side of the tip being zero, this makes the cut surfaceprone to suffering burn.

(5) TEST EXAMPLE 5

A test was performed for the above-described tipped saw of the secondembodiment. Although not illustrated, tips for side-face finishing(hereinafter referred to as a finishing tip) had a rake angle of 20°, aside clearance angle of 3°, and a peripheral clearance angle of 15°; andan outer-circumferential-side radial clearance angle of −30′ and aninner-circumferential-side radial clearance angle of 10′, which definedthe shape of side cutting edges as viewed in the front view. Tips forperipheral cutting (hereinafter referred to as rough tips) of aconventional shape had a positive radial clearance angle of 34′, a rakeangle of 20°, a side clearance angle of 1°, and a peripheral clearanceangle of 15°. Twenty finish tips and twenty rough tips were arrangedalternately and fixed to a saw blade body 11 having an outer diameter of255 mm, a saw kerf width of 4.4 mm, and a saw blade body thickness of 3mm in order to obtain a tipped saw of the present invention. Aconventional tipped saw having a saw blade body 11 having the samedimensions and forty flat tips brazed to the saw blade body 11 wasprepared as a comparative sample.

Cutting was performed at a rotational speed (of the tipped saw) of 4000rpm and a material feed rate of 5 or 10 m/min. The material of aworkpiece was wood (Japanese oak: broad-leaf tree), and transversecutting was performed. Evaluation items were center-line averageroughness Ra, ten-points average roughness Rz, and maximum height Rmaxof cut surface. Further, cutting power was measured. Table 6 showsmeasurement results. FIG. 11 shows the relationship between materialfeed rate and net cutting power; and FIG. 12 shows the cross-sectionalprofile of the workpiece cut at a material feed rate of 5 m/min.

TABLE 6 center-line ten-points manterial average average maximum feedspeed roughness roughness height (m/min) Ra (μm) Rz (μm) Rmax (μm)tipped saw of the 5 4.8 98.6 123.2 present invention 10 5.6 116.0 140.8conventional 5 6.8 116.8 148.4 tipped saw 10 8.2 135.2 188.2

The results shown in Table 6 demonstrate that the surface roughness of acut surface obtained through cutting by use of the tipped saw of thepresent invention is better than that obtained through cutting by use ofthe conventional tipped saw. Further, in each case; i.e., the materialfeed rate being set to 5 m/min and the material feed rate being set to10 m/min, the tipped saw of the present invention reduced the cuttingpower to about half that for the case of use of the conventional tippedsaw. Moreover, the cut surface had a profile equivalent to that of thetest sample shown in FIG. 9.

(6) TEST EXAMPLE 6

Forty tips 20 having a shape as shown in FIG. 13 were prepared; that is,each tip 20 had a side clearance angle of 3°, a peripheral clearanceangle of 15°, an outer-circumferential-side radial clearance angle of−30′, and an inner-circumferential-side radial clearance angle of 30′,as measured in the front view. The forty tips were brazed to a saw bladebody 11 having an outer diameter of 255 mm, a saw kerf width of 2.0 mm,and a saw blade body thickness of 1.4 mm. The saw blade body 11 had fourslots disposed at a constant pitch (center angle: 90°) and extending tothe outer circumference of the saw blade body 11 (see reference numeral61 shown in FIG. 15; the slots were provided in the tipped saws of TestExamples 1 to 5 as well). Further, an annular vibration-absorbing platemade of steel and having dimensions shown in the following Table 7 wasbonded to the saw blade body 11. A tipped saw having the sameconfiguration but not having the vibration-absorbing plate attached wasprepared as a comparative sample.

Cutting was performed at a rotational speed (of the tipped saw) of 4800rpm and a material feed rate of 2 m/min. A workpiece of wood (spruce:conifer) was cut through longitudinal cutting, and noise generated dueto the cutting was measured. The noise measurement was performed at aposition which was separated, by 1 m, from the cutting point in thehorizontal direction. FIG. 14 shows test results. In FIG. 14, darepresents the outer diameter of the vibration-absorbing plate; and dorepresents the outer diameter of the tipped saw. As is apparent fromFIG. 14, when the ratio da/do is not less than 0.8, the noise leveldecreased as compared to the tipped saw having no annularvibration-absorbing plate.

TABLE 7 outer diameter hole diameter of a vibration- of a vibration-absorbing plate absorbing plate thickness (mm) (mm) (mm) 220 180 0.25200 150 0.25 180 130 0.25 150 110 0.25

(7) TEST EXAMPLE 7

A workpiece of wood (spruce: conifer) was subjected to longitudinalcutting which was performed at a tipped saw rotational speed of 4000 to6000 rpm and a material feed rate 2 m/min by use of the same tipped sawas used in Test Example 6, and noise generated due to the cutting wasmeasured. FIG. 16 shows test results. In FIG. 16, da represents theouter diameter of the vibration-absorbing plate; and do represents theouter diameter of the tipped saw. As is apparent from FIG. 16, when theratio da/do was 0.88, the noise level could be reduced greatly ascompared to the case of the ratio da/do being 0.712, within therotational speed range of 4800 to 5300 rpm.

In the above-described embodiments, each side cutting edge has anangular shape at the inflexion point K. This portion easily wears due tocutting, with the result that the radial clearance angle becomes zero orthe portion assumes a rounded shape. Such wear is permissible if thelength of the region in which the radial clearance angle is zero or theregion of the rounded shape is not greater than the feed amount per tip(0.5 mm in this example), as shown in FIGS. 17(a) and 17(b).

In the tips according to the present invention, a relatively large loadacts on the inflexion point during cutting operation, with resultantwear in the vicinity of the inflexion point. Therefore, a hard film orhardened layer is preferably formed on at least side surfaces of thetips, or the tips are preferably made of a hard material such aspolycrystallin diamond.

INDUSTRIAL APPLICABILITY

The circular saw of the present invention is suitably used to cut a softmaterial such as wood to thereby reduce surface roughness and cuttingresistance.

What is claimed is:
 1. A circular saw comprising: tips fixed to aplurality of teeth projecting radially outwardly from the outercircumference of a disk-shaped saw blade body, wherein a side cuttingedge, which has an inflection point at a portion at which the sidecutting edge projects laterally to the greatest distance in a front viewof the tip, has a negative radial clearance angle of not less than −1°but less than 0° in the vicinity of the inflection point of the sidecutting edge and on the outer circumferential side with respect to theinflection point, and a positive radial clearance angle greater than 0°but less than 1° in the vicinity of the inflection point of the sidecutting edge and on the inner circumferential side with respect to theinflection point.
 2. A circular saw comprising: tips fixed to aplurality of teeth projecting radially outwardly from the outercircumference of a disk-shaped saw blade body, wherein a side cuttingedge, which has an inflection point at a portion at which the sidecutting edge projects laterally to the greatest distance in a front viewof the tip, has a negative radial clearance angle of not less than −1°but less than 0° in the vicinity of the inflection point of the sidecutting edge and on the outer circumferential side with respect to theinflection point, and a positive radial clearance angle greater than 0°but less than 1° in the vicinity of the inflection point of the sidecutting edge and on the inner circumferential side with respect to theinflection point, and wherein a cutting edge blade chip is formed atleast on the side surface with a hard film or a cured layer, or formedof polycrystalline diamond.
 3. A circular saw comprising: tips fixed toa plurality of teeth projecting radially outwardly from the outercircumference of a disk-shaped saw blade body, wherein a side cuttingedge, which has an inflection point at a portion at which the sidecutting edge projects laterally to the greatest distance in a front viewof the tip, has a negative radial clearance angle of not less than −1°but less than 0° in the vicinity of the inflection point of the sidecutting edge and on the outer circumferential side with respect to theinflection point, and a positive radial clearance angle greater than 0°but less than 1° in the vicinity of the inflection point of the sidecutting edge and on the inner circumferential side with respect to theinflection point, and wherein a cutting edge blade chip has a face bevelangle or zero or a positive face bevel angle.